Biological Characterization of Ovulation-Inducing Factor (OIF) in Llama Seminal Plasma

The purpose of the studies reported in this thesis was to provide a better understanding of the effects of purified ovulation-inducing factor (OIF) from llama seminal plasma in reflex ovulators (lama glama) and spontaneous ovulators (Bos taurus). The objective of the first study was to determine if the dose of OIF of llama seminal plasma required to elicit ovulation is physiologically relevant, and to test the hypothesis that CL form and function is affected by OIF in a dose-dependent manner. Llamas were treated with four different doses (500 £gg, 250 £gg, 125 £gg and 60 £gg) based on knowledge that for every ejaculate there is approximately 3 mg of OIF. Results supported the hypothesis that OIF affects ovulation and CL form and function in a dose-dependent manner. The high dose of OIF (500 ƒÝg) was associated with the highest incidence of ovulation, maximum CL diameter, plasma progesterone concentrations and plasma LH concentrations. The low dose of OIF (60 ƒÝg) was minimally effective for induction of ovulation and associated with smaller CL diameter and lower plasma concentrations of progesterone and LH. The second study was carried out to test the hypotheses that OIF will induce ovulation and affects CL form and function in cattle (Experiment 1), and that OIF given at different stages of development of the first follicular wave will induce atresia of the dominant follicle and hasten emergence of a new follicular wave (Experiment 2). Heifers were treated on Day 5 (Day 0 = wave emergence; Experiment 1) or on Days 3, 6 and 9 (Experiment 2) with a) 1ml of saline, b) 100 £gg of GnRH, or c) 1.0 mg purified OIF per 100 kg of body weight. Results of Experiment 1 demonstrated that OIF did not induce ovulation in cattle but it did induce atresia of the dominant follicle and earlier emergence of a new follicular wave. Results from the second study suggested that the effect previously demonstrated could be accomplished in sexually mature females after treatment on Day 6 corresponding to the late growing phase of the dominant follicle. In summary, the minimum dose of OIF necessary to induce ovulation in llamas was between 60 £gg and 250 £gg. This dose is physiologically relevant and represents less than 1/6th of what is normally present in a single llama ejaculate. In cattle OIF induced regression of the dominant follicle and early emergence of a new follicular wave in pre-pubertal heifers and had a similar effect in sexually mature heifers after treatment on Day 6 of the estrous cycle